U.S. patent number 4,205,336 [Application Number 05/935,005] was granted by the patent office on 1980-05-27 for signal processing system.
This patent grant is currently assigned to Sony Corporation. Invention is credited to Fumio Nagumo.
United States Patent |
4,205,336 |
Nagumo |
May 27, 1980 |
Signal processing system
Abstract
A signal processing system is disclosed for a color television
camera having a line-sequential type color coding filter provided
in a light path of an object image. An image pick-up device has the
object image focused thereon and connects to circuitry for creating
a line sequential type color output signal. First and second delay
circuits are provided for delaying the output signal and a mixing
circuit is provided for mixing the delayed color output signal and
an undelayed color output signal to obtain a mixed signal which
forms a portion of a luminance signal of the color television
camera. Another portion of the luminance signal is derived from an
output from the first delay circuit. Preferably the color output
signal represents first and second colors such as red and blue and
another line-by-line color signal is created for a third color such
as green, the green color signal being delayed in a third delay
circuit and forming another portion of the luminance signal.
Inventors: |
Nagumo; Fumio (Yokohama,
JP) |
Assignee: |
Sony Corporation (Tokyo,
JP)
|
Family
ID: |
14369008 |
Appl.
No.: |
05/935,005 |
Filed: |
August 18, 1978 |
Foreign Application Priority Data
|
|
|
|
|
Aug 30, 1977 [JP] |
|
|
52-10400 |
|
Current U.S.
Class: |
348/238;
348/E9.01 |
Current CPC
Class: |
H04N
9/04515 (20180801) |
Current International
Class: |
H04N
9/04 (20060101); H04N 009/07 () |
Field of
Search: |
;358/41,43,44-46,48 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
4059839 |
November 1976 |
Yamasaka et al. |
4065785 |
December 1977 |
Adcock et al. |
4121244 |
October 1978 |
Nakabe et al. |
|
Foreign Patent Documents
Primary Examiner: Martin; John C.
Assistant Examiner: Psitos; Aristotelis M.
Attorney, Agent or Firm: Hill, Van Santen, Steadman, Chiara
& Simpson
Claims
I claim as my invention:
1. A signal processing system for a color television camera having
at least a line-sequential type color coding filter disposed in a
light path of an object image, comprising:
(a) an image pick-up device on which said object image is
focused;
(b) means for deriving a line sequential type color output signal
alternately formed of non-delayed first and second color signals
from said image pick-up device;
(c) delay means for alternately delaying said first and second
non-delayed color signals by two horizontal scan intervals 2H, said
delay means also having a 1H delay output; and
(d) mixing means for interpolating the first color signal when the
second color signal is present at the 1H delay output by adding the
2H delayed first color signal to the non-delayed first color
signal, and interpolating the second color signal when the first
color signal is present at the 1H delay output by adding the 2H
delayed second color signal to the non-delayed second color signal,
so that said mixing means creates a mixed signal forming a portion
of a luminance signal of the color television camera.
2. A signal processing system of claim 1 wherein said delay means
includes two 1H delay devices connected in series.
3. A signal processing system of claim 2 wherein said 1H delay
output is at a junction point of said two 1H delay devices.
4. A signal processing system of claim 1, further comprising switch
means to which said 1H delay output and said mixed signal are
supplied, and said switch means having two outputs for producing
non-line-sequential color signals to be used as a portion of the
luminance signal.
5. A signal processing system as cited in claim 4, wherein said
color coding filter modifies said line-sequential type color output
signal by red color and blue color of the object image in a line
sequential manner.
6. A signal processing system of claim 4, further comprising means
for generating a green color signal of said object image line by
line, and 1H delay means for delaying the generated green color
signal, the delayed green color signal being used as a portion of
the luminance signal.
7. A signal processing system of claim 6, further comprising an
additional signal mixing means to which said non-line-sequential
color signals obtained at said two output terminals of the switch
means and the delayed green color signal are supplied for creating
said luminance signal.
8. A signal processing system of claim 6, wherein said line
sequential type color output signals comprises an (R-G) signal and
a (B-G) signal.
9. A signal processing system as cited in claim 7, wherein said
additional signal mixing means forms components of the luminance
signal.
10. The system of claim 7 wherein the line sequential type color
output signals comprise an R-G signal and a B-G signal, and wherein
means are provided for supplying the delayed green color signal,
R-G signal, and B-G signal to the additional signal mixing means in
accordance with the following respective relative levels: 1, 0.3,
and 0.11.
11. The system of claim 7 further including adder means connected
to the delayed green color signal, line sequential type color
output signal, and 1H delay output for creating components of the
luminance signal to be utilized as high frequency components;
providing a luminance signal producing adder; connecting the
additional signal mixing means through a low pass filter to the
luminance signal adder; and connecting the adder via a high pass
filter to the luminance signal adder.
12. A signal processing system as cited in claim 8, wherein said
color television camera has two pick up devices, one for green
color in all lines and the other for red and blue colors at
alternate lines.
13. The system of claim 1 further comprising means for generating a
third color signal of said object image line-by-line, 1H delay
means for delaying the generated third color signal, and adder
means connected to said line sequential type color output signal,
1H delay output, and delayed third color signal for producing
components of the luminance signal utilized as high frequency
components.
14. A signal processing system for a color television camera,
comprising:
(a) a line-sequential type color coding filter positioned in a
light path of an object image, an image pick-up device on which
said object image is focused, and means for deriving a line
sequential type color output signal corresponding to first and
second colors from said image pick-up device;
(b) means for generating a line-by-line color output signal of said
object image corresponding to a third color;
(c) first and second series connected delay means connected to
receive the line sequential color output signal;
(d) third delay means connected to receive the line-by-line color
output signal;
(e) first mixing means connected to the second delay means and line
sequential color output signal;
(f) switching means for producing non-line sequential color signals
connected to an output of the first mixing means and first delay
means; and
(g) second mixing means for producing a luminance signal connected
to an output of the switching means and an output of the third
delay means.
15. The system of claim 14 wherein the first, second and third
delay means provide a delay of 1H.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a color television camera system, and
more particularly to a color television camera system wherein red
(R) and blue (B) color signals are line-sequentially obtained from
a pickup device.
2. Description of the Prior Art
There have been proposed many types of color television camera
systems. Among them, it has been proposed to use a color filter
which has red color and blue color elements alternately aligned in
the vertical direction. In case of this system, two pick up devices
are employed for establishing the entire color television camera
system. One of two pick up devices carries the above mentioned red
and blue color filters and the other carries a green (G) color
filter. In a first approach, a luminance signal is originated by
mixing a single line signal of the green pick up device and two
lines, namely red and blue lines, of signals of the red-blue pick
up device. In such a case, low frequency components of this
synthesized luminance signal may include undesired signal
components depending on a color condition of the object. The
undesired signals are likely to be generated in the luminance
signal when blue or red color of the object is gradually changing
in the vertical direction of television scanning. FIG. 1A shows
color components of an object, wherein red and blue color
components are oppositely changed in the vertical direction. If the
output of the pick up device is smooth such as shown in FIG. 1A,
the synthesized luminance signal may also be smooth as shown in
FIG. 2A. But actually, the output of the pick up device has a
sampled signal formed by color filter elements. Also, sample
timings of blue and red color filter elements are out of phase with
each other in the vertical direction. Therefore, changes of red and
blue color components from the pick up device show waveforms
depicted in FIG. 1B. Accordingly, the synthesized luminance signal
of the prior art may include undesired components such as shown in
FIG. 2B. These will cause a dot-like pattern in the vertical
direction of the reproduced color picture.
SUMMARY OF THE INVENTION
It is a primary object of this invention to provide a new color
television camera system.
It is another object of this invention to provide a novel color
television camera system wherein line-sequentially aligned color
filter elements are employed.
It is a further object of this invention to provide a luminance
signal synthesizing system for a line-sequential color camera.
According to the present invention, the luminance signal is
generated by using an interpolation technique. Assuming that now
red filter line N is being scanned, the luminance component of the
blue color signal is generated by interpolating the blue color
signals of N-1 and N+1 lines. On the other hand, red color signals
of N and N-2 lines are interpolated for generating the luminance
components of the red color signal upon scanning the blue filter
lines of N-1. Concerning the green color signal, there is no
problem because the green color signal is obtained from all lines.
The above-mentioned synthesizing technique is preferably applied to
low frequency components of the luminance signal.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A to 1C show charts for explaining the operation of the
prior art and the present invention.
FIGS. 2A to 2C show charts for expressing the resultant luminance
signals of the prior art and the present invention.
FIG. 3 shows a well-known frame transfer type CCD imager.
FIG. 4 shows a timing chart of signals related to the operation of
the CCD imager shown in FIG. 1.
FIG. 5 shows a 2-CCD chip type color television system to which the
present invention is applied.
FIG. 6 illustrates color coding filters and their positioning
relations, relative to an image object, to be used in the system
shown in FIG. 5.
FIG. 7 shows a frequency response curve for explaining the
cancelling operation when generating high frequency components of
the luminance signal in the system shown in FIG. 5.
FIG. 8 shows a vector diagram to be applied to a chrominance signal
obtained from a modulator of the system of FIG. 5.
FIG. 9 and FIG. 10 are alternative embodiments of color coding
filters for applying this invention to another system other than
the one of FIG. 5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is applied to a two-chip type CCD
linesequential color television camera system in the embodiment of
this specification. First, an explanation is given for a solid
state imager known as a CCD imager (charge-coupled device imager).
FIG. 3 shows one example of CCD imagers. FIG. 4 shows a timing
chart of the signals related to the operation of the CCD imager
shown in FIG. 3. A 3-phase CCD s consists of a photo sensing array
1 on which a light image of an object (not shown in FIG. 3) is
projected. A temporary storage array 2 stores electric charges
corresponding to the light information of the image and a read-out
register 3 reads out picked up output signals. The arrays 1, 2 and
the register 3 are formed on a semiconductor material such as a
monocrystalline silicon substrate. The photo sensitive array 1 has
m.times.n number of picture elements aligned in the horizontal and
vertical directions at a predetermined alignment pitch La in the
horizontal direction. Each of the picture elements has one photo
sensing cell 5.
The light information of the image is converted to corresponding
electric charges at parts of a semiconductor substrate facing the
photo sensing cells 5 which are connected with electrodes CA (CA1,
CA2, and CA3) supplied with image sensing biases having a
predetermined potential during a vertical scanning interval TS.
Therefore, if a well-known transfer clock N having pulses CA which
comprises three phase phase pulses CA1, CA2 and CA3 and a following
marker signal for starting during a vertical retrace interval which
also contains a vertical synchronizing signal are applied to the
electrodes CA1 to CA3, the electric charges stored in the
semiconductor substrate corresponding to the respective picture
elements on the horizontal scanning lines are transferred to the
temporary storage array 2 and sequentially stored at the positions
corresponding to the horizontal scanning lines at every horizontal
scanning line. The temporary storage array 2 is formed similarly to
the photo sensitive array 1 but is optically shielded as a
whole.
The charges stored in the temporary storage array 2 are read out
sequentially with a read out clock pulse or sampling pulse CB which
comprises three phase pulses CB1, CB2, CB3 following a horizontal
synchronizing signal SH for each horizontal scanning period which
is applied to the read out register 3. Thus, a pick-up output
signal is derived from an output MOS transistor 4 connected to the
read-out register 3. The read-out register 3 has the same number of
read-out elements aligned in the horizontal direction and
corresponding to the picture elements of the array 1 or 2 in one
horizontal scanning line.
If a total length of the photo sensing array in the horizontal
direction is L.sub.T, then
is established.
In case of a NTSC television system, one scan duration is 63.5
.mu.sec. If a retrace interval of television scanning is neglected
for simplified understanding, a sampling duration by photo sensing
cells 5 is ##EQU1## where
fc: sampling frequency
fh: horizontal frequency of NTSC system.
FIG. 5 shows one example of a CCD color television camera system to
which the present invention is applied. In the case of this
embodiment, two CCD imagers having the same configuration as
described and depicted in FIG. 3 are employed. An object 10 is
projected through a lens 11 and half mirror 12 on both CCD imagers
13 and 14 each having a color filter 15 and 16, respectively. In
this case, respective CCD imagers are displaced by 1/2 La, namely
half of the alignment pitch of picture elements in the horizontal
direction relative to the projected image of the object 10. FIG. 6
shows the displacement of two CCD imagers with color filters 15 and
16. In the filter 15, green color elements F.sub.G are positioned
at all picture elements of the CCD imager 13, while red color
elements F.sub.R and blue color elements F.sub.B are line
sequentially positioned at respective lines of the CCD imager 14 in
case of the color filter 16. In this arrangement, from CCD imager
13, an output signal corresponding to green color information of
the object 10 is obtained from every line. On the other hand,
output signals corresponding to red and blue color information are
line sequentially obtained from the CCD imager 14. These output
signals from two imagers have a phase difference of 180.degree.,
namely half of the sampling duration. Namely, CCD imager 13
supplies the green signal G to a gamma (.gamma.) correction circuit
17, while CCD imager 14 supplies a blue signal B and a red signal R
to another gamma (.gamma.) correction circuit 18. A subtractor 19
receives output signals from both gamma correction circuits 17 and
18, and supplies difference signals R-G and B-G line sequentially
to a 1 H delay line 20 and an adder 23 functioning as a first mixer
to create interpolated R-G signals. The output of the gamma
correction circuit 17 is also supplied to a 1 H delay line 21. An
output of the 1 H delay line 21 is supplied to an adder 25 by way
of a level control amplifier 24 having an amplification factor of
1.5, so that the amplifier 24 supplies a signal 1.5 G to the adder
25. Further, there are provided two level control amplifiers 26 and
27 having an amplification factor of 0.5, respectively, The
amplifier 26 receives signal R or B from the gamma circuit 18 and
the amplifier 27 receives signal (B-G) or (R-G) from the 1 H delay
line 20. By adding three outputs from respective amplifier at the
adder 25, side band components superimposed in the base band
components are cancelled. The output of the adder 25 is expressed
as follows;
or
As mentioned before, the signal phase of signal G and signals B and
R are out of phase as shown in FIG. 7 and side band components are
cancelled. The output of the adder 25 is fed to a high pass filter
28 and is utilized as high components of a luminance signal. Of
course, the above described cancelling condition is achieved when
the object is monochrome. The output of the adder 23 is fed to a
switching circuit 30 by way of a level control amplifier 29, the
amplification factor of which is 0.5. Another input of the
switching circuit 30 is connected to the output of the 1 H delay
line 20 having interpolated B-G signals. The circuit 30 includes a
pair of switches 30A and 30B which are actuated in synchronism with
a switch pulse supplied through a terminal 31. The switch pulse is
a square wave of duty cycle 50% having a frequency of half the
horizontal synchronizing frequency. The switching circuit 30 has
two output lines 30X and 30Y. The line 30X supplies R-G and the
line 30Y supplies B-G, respectively as shown in the following
table.
__________________________________________________________________________
N: scan line at the imager 30X 30Y
__________________________________________________________________________
line N ##STR1## (B - G).sub.N-1 line N + 1 (R - G).sub.N ##STR2##
line N + 2 ##STR3## (B - G).sub.N+1
__________________________________________________________________________
These outputs appear on the lines 30X and 30Y are then fed to a
sub-carrier modulating circuit 32 to which a sub-carrier of fs is
also supplied through an input terminal 33. At the modulating
circuit 32, generally speaking, an R-G signal on the line 30X
amplitude-modulates the sub-carrier fs having a phase angle of
103.degree. advanced from the B-Y axis as shown in FIG. 8. On the
other hand, the B-G signal on the line 30Y amplitude-modulates the
sub-carrier fs having a phase angle of 13.degree. retarded from the
B-Y axis as shown in FIG. 8. In the vector analysis, color
modulated carrier signal can be considered as two vector signals.
For signal (R-G), M.sub.R and M.sub.G1 and for signal (B-G),
M.sub.B and M.sub.G2 as shown in FIG. 8. The vector sum of M.sub.G1
and M.sub.G2 becomes M.sub.G and a phase of the signal M.sub.G is
241.degree. advancing from the B-Y axis. Accordingly, three vectors
M.sub.R, M.sub.B and M.sub.G are similar to those of the NTSC color
system. The chrominance signal thus obtained is then fed to an
adder 34 and mixed with the luminance signal Y from another adder
35.
According to the invention, the low frequency components of the
luminance signal Y are generated as follows. Namely, the output of
the 1H delay 21, R-G interpolated signal on the line 30X, and B-G
interpolated signal on the line 30Y are fed to an adder 36
functioning as a second mixer, then fed to a low pass filter 37.
Therefore, the low frequency components Y.sub.L is obtained. This
signal Y.sub.L is then mixed with the high frequency component
Y.sub.H from the high pass filter 28 and resultantly, the luminance
signal Y is synthesized. As shown in FIG. 5, there is provided a
level control amplifier 38 of amplification factor 0.3, for the R-G
signal and an amplifier 39 of amplification factor 0.11 for the B-G
signal, respectively.
For the operation according to the invention of the adder 36 there
are two conditions. Namely, two kinds of signals are derived from
the adder 36 line by line. ##EQU2##
The first three terms of respective equations for Y.sub.LA and
Y.sub.LB represent luminance signal components of NTSC television
system. In this luminance signal Y.sub.LA or Y.sub.LB,
interpolation is introduced. Namely, in the line where no red
signal is obtained due to the line sequential disposition of the
color filter, the red signal is generated by interpolation of the
red signal from adjacent two lines, namely the lines of 1H after
and 1H before the corresponding line. Accordingly, as shown in FIG.
1C by black dots, interpolation is done, and therefore, as shown in
FIG. 2C, the synthesized luminance signal has almost no undesired
signal components. Further the fourth equation terms of Y.sub.LA
and Y.sub.LB, namely ##EQU3## for Y.sub.LA and ##EQU4## for
Y.sub.LB respectively, serve to improve the resolution in the
vertical direction. Therefore, an aperture correction signal is to
be added to the luminance signal.
The above-described embodiment was provided in a system in which
two CCD imagers with non-interlace scanning are employed. In the
case where 2:1 interlace scanning is introduced, the color filter
16 in FIG. 6 should be modified as shown in FIG. 9.
Further in the case where only one CCD imager is employed, the
color filter 16 may be modified as shown in FIG. 10. In these
alternative embodiments, the CCD imager has to accept interlace
scanning operation, if the system requires interlace scanning.
Needless to say, this invention is applicable to any pick up device
such as a photo diode array, photo transistory array, and even to a
vidicon type camera system. A necessary requirement for applying
this invention is that the color coding filter is arranged in a
line sequential manner with respect to two color components.
Incidentally, a terminal 40 in FIG. 5 receives a composite sync.
signal, and 41 is a system output.
Although various minor modifications may be suggested by those
versed in the art, it should be understood that I wish to embody
within the scope of the patent warranted hereon, all such
embodiments as reasonably and properly come within the scope of my
contribution to the art.
* * * * *